Wireless networking standards may be defined with varying data rates, modulation techniques, frequencies, number of antennas, and other parameters. A newer standard is often backward compatible with older standards so that existing equipment designed for use with older standards may still be used with equipment deploying the newer standard. For example, the older IEEE 802.11b standard defines operation in the 2.4 GHz band at data rates of 1, 2, 5.5, and 11 Mbps using a single antenna. The digital modulation scheme varies with the data rate in the 802.11b standard. The modulation scheme used at 1 Mbps or 2 Mbps is a direct-sequence spread spectrum scheme (DSSS), which includes phase shift keying (PSK) and differential phase shift keying (DPSK), while at 5.5 Mbps or 11 Mbps, a complementary code keying scheme (CCK) may be used. On the other hand, the newer IEEE 802.11n standard defines operation in the 2.4 or 5 GHz bands at multiple data rates up to a maximum of 600 Mbps using multiple antennas in a spatial multiplexing approach, known as a multiple input, multiple output scheme (MIMO). The 802.11n standard may use the DSSS, PSK, DPSK, and CCK modulation schemes to maintain backward compatibility, and may also use additional modulation schemes, such as orthogonal frequency division multiplexing (OFDM) and quadrature amplitude modulation (QAM). Other wireless networking standards exist, such as 802.11a and 802.11g, which may have other data rates, modulation techniques, frequencies, and other parameters.
Wireless networking equipment using the 802.11b standard may operate in environments with wireless networking equipment using the 802.11n standard. For example, a receiver with multiple antennas designed primarily for use with the 802.11n standard may receive a radio frequency (RF) signal conforming to the 802.11b standard. If an 802.11n signal is received by the 802.11n receiver, each antenna may receive a unique stream of data packets, as defined by the 802.11n standard, to take advantage of the multiple antennas. However, if an 802.11b signal is received by an 802.11n receiver, each antenna receives an 802.11b signal with the same data packets on each signal, because the 802.11b standard does not define the use of multiple antennas. In this situation, the received 802.11b signals may be of differing qualities on one antenna compared to another antenna, due to the effects of multipath delay, interference, and other factors. Existing 802.11n receivers receiving an 802.11b signal may randomly select an antenna to use or may be restricted to using one antenna for processing 802.11b signals, which may result in the use of a lower quality signal. If a lower quality signal is used, the performance of the wireless network and/or the equipment may decrease. In addition, an 802.11n receiver receiving an 802.11b signal may use conventional antenna selection in the RF domain to select an antenna out of the multiple antennas, but such receivers may be slower and put an increased hardware burden on the receiver. Therefore, there is a need for fast intelligent selection of an 802.11b signal in a wireless networking receiver with multiple antennas.